function sameSing(a,b){
	return (a^b)>=0
}

function vector(a,b){
	return{
		x:b.x-a.x,
		y:b.y-a.y
	}
}
function vectorProduct(v1,v2){
	return v1.x*v2.y-v2.x*v1.y
}


function isPointInTrangle(p,a,b,c){
	var pa=vector(p,a)
	var pb=vector(p,b)
	var pc=vector(p,c)

	var t1=vectorProduct(pa,pb)
	var t2=vectorProduct(pb,pc)
	var t3=vectorProduct(pc,pa)

	return sameSing(t1,t2)&&sameSing(t2,t3)
}
function needDelay(elem,leftCorner,currMousePos){
	var offset=elem.offset()
	var topLeft={
		x:offset.left,
		y:offset.top
	}

	var bottomLeft={
		x:offset.left,
		y:offset.top+elem.height()
	}

	return isPointInTrangle(currMousePos,leftCorner,topLeft,bottomLeft)
}



//这个是需要理解差乘公式！